This invention relates to a method of and a system for converting heat energy of a relatively low temperature into energy of a relatively high temperature, and more particularly to a heat energy conversion method and a system therefor, in which energy conversion is effected more effectively between energies of a small temperature difference.
As methods of recovering heat energy of a low temperature level and converting it into energy of a high temperature, there are various methods. In these methods, a method which employs a so-called absorption heat pump is known.
In the method, a high-boiling liquid (for example, LiCl liquid) diluted with a low-boiling liquid (for example, H.sub.2 O) is concentrated up to C.sub.2 % through evaporation with energy of low-temperature T.sub.2 at a pressure P.sub.1 which is the vapor pressure of the low-boiling liquid to a temperature T.sub.1 (&lt;T.sub.2). The vapor generated in this step of evaporation is condensed by energy of low-temperature T.sub.1 at the pressure P.sub.1. The condensed low-boiling vapor is heated and evaporated by energy of low-temperature T.sub.2 at the pressure P.sub.2 which is the vapor pressure of the low-boiling liquid to the temperature T.sub.2. The vapor is absorbed into the concentrated high-boiling liquid at the pressure P.sub.2 and diluted to C.sub.1 %, and here the dilution heat of the high-boiling liquid and the phase-change latent heat are generated so that the heat medium has its temperature elevated up to the saturation temperature T(T.sub.1 &lt;T.sub.2 &lt;T) of concentration C.sub.1 % under the vapor pressure P.sub.2.
As described above, the method can exploit the dilution heat of the high-boiling liquid and the phase-change latent heat of the low-boiling vapor, the thermal efficiency therefore is high. However, the highest rise temperature T' is limited by the concentration C.sub.1 % of the high-boiling liquid and the pressure P.sub.2 at that time. Accordingly, when the temperatures (T.sub.1, T.sub.2) of the relatively low-temperature energies are low, and the temperature difference .DELTA.T(T.sub.2 -T.sub.1) of both the energies is small, the pressure P.sub.2 also becomes small and the concentration C.sub.1 becomes low, resulting in the disadvantage that the highest rise temperature becomes low.